Ontario Division of Industrial Hygiene to W. A. Young on Dust Counts at the Port Union Plant (1949)

A one-page letter of September 27, 1949, with a page of dust counts, from an engineer of the Division of Industrial Hygiene at the Parliament Buildings in Toronto to W. A. Young of Canadian Johns-Manville at Port Union, Ontario, reporting samples from five places in the plant's Transite pipe operations. The division treated the first place, the hopper fed with asbestos fibre and portland cement, as straight asbestos exposure with a maximum allowable of 5 million particles per cubic foot, and the other four as dust of 25% asbestos with an allowable of 20 million. The counts ran from 6.3 to 16.7 million, and the letter recommended further study of the equipment at the charging end and better local exhaust at the dry sawing and machining.

In Johns-Manville's chronology

Johns-Manville's own chronology of what the company knew describes this document as follows:

The Toronto Government conducted an industrial hygiene survey at the Toronto plant, 9/27/49. The government applied the 5 mppcf standard when the product contained 100% asbestos and 20 mppcf when it contained 25% asbestos. It encouraged J-M to make some improvements at the charging end to reduce to a minimum dust at the dry sawing and machining. It stated that, even though these stations were below TLV, dust is unpleasant.

Editor's note: J-M's description says the stations were below the limit. The sawing and machining stations were below the 20 million particle limit the division applied to them, but the count at the charging hopper, 10.2 million, was above the 5 million limit applied there.